Tires should be replaced before or at 10 years of age. A tire at 10 years old or older is basically a ticking time bomb and is just waiting to blow out on you which could cause you to roll your vehicle and could potentially kill you.
You should periodically inspect your tires for weather checking and cracks or bulges in the tire.
If your tire has bulges also known as a tire hernia you should get the tire replaced asap as it means the tire is about to blow out.